Your Purple Maiden Grass, Miscanthus sinensis 'Purperescens', should be trimmed back just before the new growth begins to emerge. The exact time is different every year, so just watch your plant and then give it a buzz haircut, not straight across, but trim it in a rounded shape about 6" above the dense center of the plant. You have probably seen yards with grasses trimmed in a huge fall 'cleanup,' resulting in yards that have lost their charm, and their wildlife value as well. Since you allowed your grass to stay intact through the winter it added interest and structure to your landscape, and it provided cover for wildlife.
Some forms of Maiden Grass are considered to be invasive in many Eastern states and in Tennessee and Michigan, so keep your eye on it. If it appears to be spreading, then I recommend that you remove the plant(s) and opt for a native grass instead.
Blue Arctic Willow, Salix purpurea is a thicket-forming shrub that favors moist growing conditions and it too has the potential for becoming invasive. Currently monitored in riparian areas where this willow is used for erosion control, in Oregon for example, folks in Colorado probably should play it safe and avoid planting it near streams and wetlands. All too often plants that grow too quickly and too well, introduced from other parts of the world for erosion control, are the culprits that make our lists of noxious plants. In your poolside situation there should be no problem, but I thought you would be interested in knowing about this.
The Blue Arctic Willow is naturally dense and retains its rounded form without too much maintenance. In late winter, while the plant is still dormant, remove any 'wild hairs' and old branches according to the recommendations found in a guide from the University of Wisconsin Cooperative Extension. Have a beautiful spring season!